In recent years, the vertical trellising of grapevines has become more important, particularly in connection with varieties such as Chardonay, for which it is advantageous to support the foliage in an elevated position relative to the grapes or berries. So-called "vertical" trellising systems employ a pair of trellis wires which are positioned with one wire lying on the ground at the base of each side of the grape stakes along the row of vines. After the foliage is nearly fully formed and the berries begin to form, the trellis wires are lifted from the base of the stakes to a support device, such as a transversely-extending armor wire assembly mounted on the grape stakes. As the trellis wires are raised, they catch the grapevine foliage and move it to an elevated position above the berries. This exposes the berries to more direct sunlight, which is helpful to berry development.
Trellis wires have been supported from grape stakes for vertical trellising using both short, transversely-extending metal arms and wire-based support assemblies. Such metal arms usually have openings which receive the trellis wire, and one example of a metal trellis wire support arm used in vertical trellising is shown in U.S. Pat. No. 4,965,961 to Broyles. Another more elaborate metal arm trellising system is disclosed in U.S. Pat. No. 5,144,768 to Hiyama.
Two prior art wire-based trellis wire support assemblies which have been used, particularly in France, are shown in the brochure of SCDC, a French trellising hardware company. These wire-based assemblies are formed with transversely-extending wire arms that terminate in upwardly-extending ends to provide a goal post-like structure over which the trellis wires may be laid and supported. Other wire-based trellis wire support assemblies found in the patent literature include U.S. Pat. Nos. 115,662, 1,060,593, 1,851,224, 4,099,299 and 4,270,581.
The number of trellis wire support assemblies required for vertical trellising makes it highly advantageous to be able to reduce the cost of manufacturing and supporting trellis wires from grape stakes. Wire-based support assemblies have an inherent cost advantage over stamped metal arms or clips. Such wire-based support assemblies, however, also have experienced various disadvantages such as tedious and costly installation, an inability to easily mount and remove the trellis wires from the wire support assembly, and an inability to retain the trellis wires when an upward loading force is present on the wires. This latter problem is present in the French wire-based assemblies and the assembly of U.S. Pat. No. 1,060,593. Since many vineyards are in rolling terrain, the trellis wires which extend down into valleys or depressions are loaded in an upward direction. Moreover, the wind loading on foliage can be substantial and can lift the foliage and the trellis wires out of goal post-type trellis wire support assemblies.
Accordingly, it is an object of the present invention to provide a wire-based trellis wire support assembly which is low in cost and yet capable of retaining trellis wires against both upward and downward loading.
Another object of the present invention is to provide a wire-based trellis wire support assembly which can be installed in rolling terrain on both knolls and valleys for vertical trellising of grapevines.
Still a further object of the present invention is to provide a trellis wire support assembly to which movable trellis wires can be easily mounted and easily removed.
A further object of the present invention is to provide a wire-based trellis wire support assembly which can be easily installed on grape stakes using simple tools and yet provides a durable, low maintenance, high strength structure.
The trellis wire support assembly of the present invention has other objects and features of advantage which will become apparent from, and are set forth in more detail in, the accompanying drawing and the following Description of the Best Mode of Carrying Out the Invention.